Questions tagged [antenna]

Questions about the design, selection, building, testing, mounting, or properties of antennas. See also specific tags: [antenna-theory], [antenna-construction], [dipole], etc.

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45 views

Passive receiver power needs & data rate

I'm working on a project to design a space-based low frequency array. It will only be receiving signals, and it will operate between 10MHz - 100MHz. It is made of short wave crossed dipole antennas. I ...
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1answer
69 views

why is 3rd order intermodulation for 2110-2155 = 1710-1755?

Trying to calculate 3rd order intermodulation for a frequency range (2110 to 2155). I know the answer is 1710 to 1755, but I don't know how to get there. attempts: ...
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129 views

Can the Q of a loop antenna be changed?

Can the Q of a loop antenna be changed? If so what are some common techniques? (Formulae appreciated).
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1answer
596 views

How to assemble an antenna (impedance matching methods)

I got the following plans off Martin E. Meserve's website. How do I go about assembling the antenna once I have the elements and boom? What is the impedance of the driven element? Do I need baluns ...
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2answers
160 views

Serial matching stub combined with RF choke

If I use RG6 coaxial cable in odd multiples of 1/4 wavelength as a serial matching stub, can I also use it, without modifying the length, as a coiled RF choke balun at the antenna feed point?
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1answer
651 views

Best way to make a selfmade Long-Range WiFi Link

What needs to be considered? Which type of antenna(only self-made or reused parts, for example satellite dish) is the best for a long range, high throughput WiFi? How to calculate Antenna size and ...
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1answer
96 views

Antenna for 6M, or Antenna system?

Here, in VU-land, 6M allocation is from 50 MHz through 54 MHz... which is a fair chunk of spectrum. If I think about a half-dipole antenna; between 50/54 MHz it's length varies by over a foot ... and ...
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1answer
826 views

VHF / UHF - Terrestrial Circular Polarized Antenna

I've been doing mostly HF for the last 20 years and just recently installed a 2m/70cm mobile rig in my shack for base station work. I like to work FM simplex and repeaters when the HF bands are not ...
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1answer
288 views

Determining the correct sidelobe envelope

I need to determine the correct sidelobe envelope for various VSAT antennas. Given the radiation pattern (this one, for example http://www.gdsatcom.com/vsat/technical_docs/patterns/6000-023.pdf), how ...
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1answer
153 views

Wideband impedance matching

I'm using an antenna that works in the range from 1 GHz to 3 GHz. I want to match impedances between a cable from the transmitter and the input amplifier and from the output amplifier and the cable to ...
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2answers
338 views

Antenna + LNA Design Questions

I am trying to design and build an antenna + LNA board. Antenna: http://www.yageo.com/documents/recent/An_FR4_1690_2405_0.pdf LNA: http://www.avagotech.com/docs/AV02-1237EN The antenna is specced ...
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1answer
138 views

Magnum 257 & Firestik 3' Tuning

Trying to tune a Firestik antenna connected to Magnum 257 on my '98 Jeep Wrangler. Having trouble with SWR reading as it is reading too high (~4) after I set needle on FWD and then switch back to REF. ...
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1answer
581 views

In which direction should single wire antenna in underground parking be pointed?

In our collective building lot we have an underground parking, in which a company recently changed a functional garage door system, since then the reception is a lot worse than before. (Like it doesn'...
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1answer
444 views

What is the best resonator in Yagi antennas?

As we saw many design for this Yagi feed point. Q1 . Which one would be the best resonator / driven? Gamma match, T-match, delta match, folded dipole, quad, loop? Q2. And what is the reason if ...
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2answers
2k views

How to make a loop antenna for HF?

While researching this answer, I came across information that indicates that a many good Low Frequency/ Very Low Frequency antennas are loops, with high directionality and good overall characteristics....
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1answer
3k views

Homebrew 2 meter Yagi construction

Here is what I have • A Baofeng Uv-82 transceiver • A 1/2 inch 10 foot PVC pipe • 3 1/4 inch x 36 inch Aluminum rods • 2 1/4 inch x 48 inch Steel rods (I know they'll rust, it's just temporary to ...
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3answers
101 views

Why do we need special geometry for telecommunication antennas?

In many youtube videos about building low power radio transmeters , I have seen a piece of regular wire or extension cord used as a antenna. But , it seems like telecommunication antennas have ...
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0answers
37 views

How to cut phasing/transformer coax in a right way?

I'm building RHCP crossed dipole for 137 MHz satellites reception (I'm using 137.5 as a central frequency). My calcs are: frequency is 137.5 MHz λ is 2.18 m one dipole leg length equals to the λ/4 so ...
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1answer
95 views

Is this antenna “system” really work? [closed]

I posted yesterday asking how can I have signal inside my house which my house is obstructed by a hill from direct signal from the cellular's operator' Base Transceiver System (BTS). The schema of the ...
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0answers
88 views

How do I Construct a Simple FM Antenna?

I recently bought a cheap stereo amplifier with built in FM receiver from Amazon at the first link below. Testing it out today I found the FM reception to be sub-par. All of my local stations that I ...
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0answers
39 views

Problem to paralel tv digital reciever [closed]

Here is my C-Band parabolic tv digital receiver. As shown by the pictures, the incoming coax cable (INPUT) connected both the outer and the core. One goes to digital receiver 1 (receiver 1), and ...
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0answers
66 views

What should I take into consideration when choosing a new antenna? [closed]

I am trying to choose a new antenna for the HackRf One, but there are several variables to consider, such as the frequency, threading, resistance etc. In general, what things should I take into ...
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0answers
38 views

Unsure how to assemble Shakespeare SSB antenna; not working [closed]

Have 23 foot Shakespeare SSB antenna. Can not connect through the side feed termination band? Antenna not working? What is the band supposed to look like? Is the termination band supposed to be ...
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0answers
77 views

Can a radio antenna damage a phone? [closed]

I am currently attending a radio technology course. We continuously work on radio sets that are sometimes used as manpacks by the Army. In order to learn how to operate them we work in close proximity ...
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0answers
102 views

Antenna Impedance calculation for low frequency [duplicate]

If I have an end fed long wire in free space, say 100 ft, how do I calculate its $R$ & $X$ at different frequencies?
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88 views

OCF Antenna Feed Line [closed]

I built a OCF HF antenna. The feed line contains a 4:1 balun and a line insolator (choke) per instructions. When checking the radio end of the coax, I get a "grounded" response between the inner wire ...
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0answers
254 views

What will be antenna impedance of a dipole antenna when it is kept lambda/2 away from the transmitter

I understand that half-wave dipole antenna, which is in far-field, impedance is around 73 ohms. If I keep same antenna in near-fied at distnace lambda/2 from the 1.25 lambda length tranmiter?
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0answers
57 views

Interpreting the Friis transmission equation [duplicate]

In the Friis transmission equation, can you please explain the significance of the factor $$\left(\frac{\lambda}{4\pi R}\right)$$ and what it helps us achieve? Specifically in terms of path loss.
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0answers
85 views

Best frequency for very local dense building chat [closed]

Let's say everyone has general liscense classes and can erect antennas to whatever can fit on the human body. What would be the best frequency to talk locally in an area with lots of buildings and man ...
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0answers
219 views

Designs for a multi band vertical/collinear antenna for the 1.9 gigahertz range [closed]

I'm starting to research building a multi-band antenna in the 1.9 gigahertz range. I see them offered on wireless routers, and they use them in cellular sites. Can anyone provide a reference or quick ...
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9answers
673 views

Explain how an antenna works to an 18 year old

It's either math or magic. It seems like the only thing that will explain operation are complex formulas. If a child were to ask "how does an antenna work" what should one say, it magically changes ...
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2answers
373 views

Antenna Basics - Open/Short Circuit & Half-Duplex/Full-Duplex

I am beginner in the Antenna theory and I have a few basic questions. Please help me to clarify my understandings related to the basics which I have read. And this question has 3 basic questions. ...
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2answers
4k views

DIY 433MHz antennas from copper wire

I need to build two minimalistic antennas for RX/TX at ~433MHz. I have insulated solid core copper wire, but I need to make it perfectly straight. I was thinking of using the type of sticks you set ...
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2answers
184 views

Should a MacBook emit fluctuating EMF when WIFI and Bluetooth are turned off?

I have a couple of MacBooks. Using a Trifield EMF meter with radio/microwave capability, if I hold the meter near the laptop (where I understand the wifi antenna is located), I receive blips ranging ...
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3answers
80 views

What is minimum resolution for 2 frequencies to interfere each other

I started working with HF frequency. Right now, I am working with 7 MHz frequency. I have been provided a range of 7-7.5 MHz. I have to divide that range into 132 distinct frequencies to assign each ...
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3answers
304 views

To folded dipole, or not to folded dipole?

I currently operate a 20M half-wave dipole with a balun. It's a little lower than ideal, but it gets me on the air. I've read about folded dipoles. But I've found contradicting information about them....
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1answer
138 views

Vertical Antennas

I have just changed from a ground mounted Vertical antenna , to a MFJ-1796 Vertical antenna, due to not having big enough ground to bury as many verticals as recommended. So far what I have found is ...
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2answers
1k views

Understanding RG6-75 ohm Cable Impedance

Here is my measurement to a piece of RG6 cable. It is around 30cm cable. On the shield is written COAXIAL CABLE 5C-2V 75 ohm. From my measurement I got data as below: From that table, we can see that ...
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3answers
2k views

Will two ends of dipole antenna pointing to the same direction cancel out the signal

I am living in a small compartment, considering setting up an antenna indoors. As my room is so small (3m^2), thinking of putting a dipole antenna with soft wire indoors. If two ends of dipole ...
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1answer
21 views

Is this result correct ? [ impedance cavity based on emtamaterials using CST Microwave]

In the contexte of my reaserch about antenna conceptions, I'm trying to simulate using CST Microwave a cavity antenna based on metamaterial structure and a slot antenna as a GND,However I got as a ...
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2answers
167 views

How to use 75ohm (RG6) coax?

I know that there have been many similar threads on this, but I still need clarification. At the moment, the only thing I have is a 500' roll of RG-6 and a (very) tight budget, and I should be ...
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2answers
249 views

Loop on ground for transmit?

If a large horizontal loop antenna, insulated but laying at ground level, works as an MF and low HF receive antenna, why (even though it has very high ground losses) can't it be used for transmit (to ...
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2answers
1k views

If one were to add reflector elements above and below a dipole would it change the direction to horizontal?

Since adding a reflector and a director horizontally to a dipole (as in a three element Yagi) causes the beam to reflect horizontally, what should happen if reflectors above and below the dipole were ...
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2answers
68 views

Tuning two antennas using wire length

I've heard that in the early spark-gap wireless telegraphy era people would use kites with a wire acting as antennas and if the receiving side had a wire length that was an even division or multiple ...
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2answers
112 views

1/8 wave 3-element 2m beam antenna

Here's what I am working on, and someone please tell me if I'm doing this right or wrong, but be kind and gentle. Center frequency 146.520MHz Driven element is 1/8 wave 10.25" long set at 6.125&...
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3answers
89 views

How does a smartphone FM antenna work?

My understanding is the earbuds that connect to the aux port act as the antenna. It's a long wire. The problem is that the same wire is being used to power your earbuds so you can hear the radio ...
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1answer
56 views

Stacked Yagi Gain calculation

I had a quick look at a practice exam for the license in my country and had a question on stacked Yagi antenna. I have been looking around but the only thing I can find is the mention of an additional ...
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4answers
432 views

Building an AM Radio receiver

I am making an AM radio with the specifications of: Part 1. Design a circuit with an antenna for tuning your receiver to a signal of a specific carrier radio frequency so that you can select a certain ...
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1answer
100 views

How to characterize and select UHF linearly loaded antennas?

Q1.1: Why can a helix calculator not be used for linearly loaded antennas? Those online calculators suggested that the turn pitch/wavelength should be around 0.25. However, a typical linearly loaded ...
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3answers
3k views

Can I test a base station CB radio with a magnetic mobile antenna?

I am looking at a base station and want to test it before purchasing can I use a magnetic mobile antenna to see if it transmits and receives without damaging it?